Benign Prostatic Hyperplasia (BPH) can cause urinary frequency, dysuria and incomplete bladder emptying. The surgical “gold standard” for treating BPH has been the transurethral electrosurgical resection of obstructing prostatic tissue. Since its introduction some 50 years ago, transurethral resection of the prostate (TURP) has become the most widely used surgical therapy for BPH. Unfortunately, TURP associates with numerous side effects.
In the past decade, laser prostate surgery has become an alternative option to treat BPH, which troubles effected men with symptoms such as urinary frequency, dysuria and incomplete bladder emptying. In laser prostate surgery, a high power laser beam may be delivered to target prostate tissue through an optical fiber that is introduced through an endoscope or cystoscope. The effectiveness of this treatment for BPH (or for the removal of other soft tissue) may depend on a number of factors, including wavelength, power density, pulse duration, pulse fluence and/or other factors.
Conventional laser ablation systems implemented in laser prostate surgery may include high average power (60-80 W) Nd:YAG laser with a wavelength of 1064 nm. The electromagnetic radiation emitted by these systems may heat up the laser-irradiated tissue to boiling temperature. This may evaporate a top layer of the tissue and coagulate an under layer of the tissue. The conventional systems tend to employ Nd:YAG lasers because they may be capable of emitting electromagnetic radiation with an enhanced hemostatic effect. For example, the radiation may penetrate the tissue to a 7 mm penetration depth. But, with the Nd:YAG systems, this penetration may create a thick layer of tissue coagulation. For this and other reasons, conventional systems employing an Nd:YAG laser may not be as effective as TURP in the treatment of obstructive BPH.
Other conventional systems for ablating soft tissue, such as prostate tissue have implemented high power (60-100 W) Ho:YAG lasers with a wavelength of 2140 nm. Electromagnetic radiation produced by these systems may by absorbed by water, and can thus evaporate soft tissue effectively. Under limited circumstances, Ho:YAG laser surgery may produce a clinical outcome comparable with TURP. However, Ho:YAG laser surgery may provide various technical problems, and may not currently be practical for widespread usage.
In still other conventional systems, a 60 W average power, Q-switched and frequency-doubled Nd:YAG laser may be used for the ablation of soft tissue in BPH treatment. In these systems, the laser may be lamp pumped to produce quasi-CW Q-switched pulses at 532 nm. Electromagnetic radiation at this wavelength is transparent in water but may be selectively absorbed by oxyhemoglobin in soft tissue. These systems may effectively vaporize and ablate soft tissue and concurrently achieve some level of hemostasis. The surgical outcome is comparable with TURP while the complication is significantly reduced. However, as with the Ho:YAG systems, technical problems with the implementation of an Nd:YAG laser in a clinical system for ablating soft tissue exist.
For example, the power conversion efficiency of these systems may be relatively low. In some instances, this efficiency may be below 3%. This may require these systems to include a special power source, as they may not be efficient enough to run off of a power supply provided by a standard wall outlet (e.g. a 110V outlet, a 220V outlet, etc.).
As another example, Nd:YAG lasers, as well as the Ho:YAG lasers, typically implement a solid state gain medium, which may dissipate an elevated amount of energy as heat. Thus, in order to avoid damaging components of the laser ablation systems that employ these types of lasers, the systems usually must incorporate an extensive cooling system. For example, these cooling systems may include liquid cooling systems and/or secondary cooling loops. These extensive cooling systems may require additional power, be bulky and/or unwieldy, an/or provide other drawbacks.
Other drawbacks associated with these and other conventional systems that use lasers to ablate soft tissue exist.